Investigation of the biogeochemistry of methane and mechanisms of its transfer in the Black Sea

Sovga, Elena; Lyubartseva, S. P.; Lyubitsky, A. A.

doi:10.1007/s11110-009-9024-z

Cited by 3 publications

(3 citation statements)

References 16 publications

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“…Зміни початкових параметрів газовиділення при спливанні враховуються за допомогою моделі [16,34] Система диференціальних рівнянь, що описують модель, чисельно інтег рується з використанням модифікованого методу Рунге Кутта при заданих фоно вих параметрах середовища, глибині джерела і початкових розподілах бульбашок за розмірами і швидкостям спливання. Передбачається, що в момент відриву від дна газові бульбашки містять тільки метан.…”

Section: опис моделіunclassified

Simulation model of sound backscattering in gas flares and evaluation of the potential accuracy of determining seep coordinates by split-beam echosounders

LYUBITSKIY¹,

Omelchenko²

2022

Geol. polezn. iskop. mirov. okeana

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A simulation model of sound backscattering in gas flares is presented, designed to solve direct and inverse problems of acoustic sensing of flares using the simulation (computer) modeling method. The model is based on the concept of the discrete character of sound scattering in a gas plume, according to which the received echo signal is the sum of elementary signals, backward-scattered bubbles that form the flare. At the same time, the model of sound reverberation in a gas flare is considered as a temporary random process in the absence of multiple scattering effects. The model takes into account the distributions of gas bubbles by sizes and rise velocities, as well as the evolution of bubbles and their gas exchange with the marine environment during ascent. Based on this, the potential accuracy of deter- mining the coordinates of gaseous sources (seeps) by a split-beam echo sounder was estimated by simulation modeling. It has been established that the main parameters that determine the RMS (root- mean-square deviations) of the estimates from the actual coordinates are the transverse size of the flare near the bottom, the SNR (signal-to-noise ratio), and the volume of echo signal samples. Dependences of the RMS on the determining parameters are obtained.

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Section: опис моделіunclassified

Simulation model of sound backscattering in gas flares and evaluation of the potential accuracy of determining seep coordinates by split-beam echosounders

LYUBITSKIY¹,

Omelchenko²

2022

Geol. polezn. iskop. mirov. okeana

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“…Previous Black Sea methane studies have highlighted a variable vertical concentration distribution (McGinnis et al, 2006;Schmale et al, 2010;Sovga et al, 2008), with increasing values while going from the oxic into the anoxic water layer. So, methane concentrations up to 12 nmol L −1 were measured in the oxic layer, and in some areas, the sea surface was oversaturated in methane with respect to the atmosphere (Malakhova et al, 2010;Reeburgh et al, 1991).…”

Section: Introductionmentioning

confidence: 99%

Inter-Comparison of the Spatial Distribution of Methane in the Water Column From Seafloor Emissions at Two Sites in the Western Black Sea Using a Multi-Technique Approach

et al. 2021

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Understanding the dynamics and fate of methane (CH4) release from oceanic seepages on margins and shelves into the water column, and quantifying the budget of its total discharge at different spatial and temporal scales, currently represents a major scientific undertaking. Previous works on the fate of methane escaping from the seafloor underlined the challenge in both, estimating its concentration distribution and identifying gradients. In April 2019, the Envri Methane Cruise has been conducted onboard the R/V Mare Nigrum in the Western Black Sea to investigate two shallow methane seep sites at ∼120 m and ∼55 m water depth. Dissolved CH4 measurements were conducted with two continuous in-situ sensors: a membrane inlet laser spectrometer (MILS) and a commercial methane sensor (METS) from Franatech GmbH. Additionally, discrete water samples were collected from CTD-Rosette deployment and standard laboratory methane analysis was performed by gas chromatography coupled with either purge-and-trap or headspace techniques. The resulting vertical profiles (from both in situ and discrete water sample measurements) of dissolved methane concentration follow an expected exponential dissolution function at both sites. At the deeper site, high dissolved methane concentrations are detected up to ∼45 m from the seabed, while at the sea surface dissolved methane was in equilibrium with the atmospheric concentration. At the shallower site, sea surface CH4 concentrations were four times higher than the expected equilibrium value. Our results seem to support that methane may be transferred from the sea to the atmosphere, depending on local water depths. In accordance with previous studies, the shallower the water, the more likely is a sea-to-atmosphere transport of methane. High spatial resolution surface data also support this hypothesis. Well localized methane enriched waters were found near the surface at both sites, but their locations appear to be decoupled with the ones of the seafloor seepages. This highlights the need of better understanding the processes responsible for the transport and transformation of the dissolved methane in the water column, especially in stratified water masses like in the Black Sea.

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“…The CH4 emission into the atmosphere from all marine sources, including the open ocean, continental shelf, estuaries and seeps of the continental borderlands, is estimated at CH4 8.3-45.9 Tg per year [1]. Among the inland seas, the Black Sea is one of the most powerful methane reservoirs; many works have been devoted to the study of the biogeochemistry of the methane cycle in its water area [2][3][4]. The methane sources in the Black Sea are microbial production in bottom sediments and the water column, as well as methane gas emissions, which are widespread along the entire Black Sea shelf.…”

Section: Introductionmentioning

confidence: 99%

Features of Methane Distribution in the Euphotic Layer of the Northern Black Sea in Summer, 2018 (Based on the Data of the 102nd Cruise of R/V "Professor Vodyanitsky")

Малахова¹,

Мансурова²,

Malakhova³

et al. 2020

PhO

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The main goal of the work was to assess the horizontal and vertical structure of methane (CH4) distribution, its emission to the atmosphere in the euphotic zone of the northern part of the Black Sea in summer, 2018 as well as to reveal its relationship with the chlorophyll a concentration. Methods and Results. The CH4 concentration in the surface layer was determined by the gas chromatographic method at 104 stations, including 45 stations at which the vertical profiles of the CH4 content in the upper 0-50 m layer were done. The chlorophyll a concentration was defined by the fluorometric method. The CH4 distribution in this region showed distinct spatial heterogeneity. The concentration of the dissolved in the surface water CH4 varied within 0-39.2 nmol/l at all the stations. The average calculated value of the CH4 seawater-air flux was 2.3 nmol/m 2 /day, and the average CH4 saturation of surface water -460 %. The major part of the sea area under study represented a source of methane emission to the atmosphere near-water layers, except for 15 stations where the CH4 concentration in the surface layer was smaller than its equilibrium values. The calculated integral value of the CH4 flux from the whole region under study (its area is equal to 88•10 3 km 2 ) constituted 3.2 tons of CH4 per day. Vertical distribution of CH4 in the upper 50 m layer was different in the coastal and deep-sea areas. At the deep-sea stations, the maximum values were revealed in the sub-surface layers, whereas at the coastal stations (not deeper than 100 m), the highest CH4 concentrations, up to 86 nmol /l, were observed mainly at the near-bottom horizons. Conclusions. The average concentration of CH4 in the deep-sea profiles was 2 times lower than that in the coastal ones. Sub-surface maximums of the CH4 concentration coincided in general with the maximums of the chlorophyll a concentration. It was also found that the CH4 highest concentration corresponded to the increased chlorophyll a content (0.58 mg/m 3 ) in the Feodosiya Gulf surface water. The abnormally high concentration of CH4 (269 nmol /l) at the bottom horizon, by an order of magnitude exceeding the average methane content in the adjacent areas, was revealed at the station near the Dnieper paleo-channel. Such an increased concentration is assumed to be caused by the methane emission from the gas seeps densely located in this region.

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Investigation of the biogeochemistry of methane and mechanisms of its transfer in the Black Sea

Cited by 3 publications

References 16 publications

Simulation model of sound backscattering in gas flares and evaluation of the potential accuracy of determining seep coordinates by split-beam echosounders

Simulation model of sound backscattering in gas flares and evaluation of the potential accuracy of determining seep coordinates by split-beam echosounders

Inter-Comparison of the Spatial Distribution of Methane in the Water Column From Seafloor Emissions at Two Sites in the Western Black Sea Using a Multi-Technique Approach

Features of Methane Distribution in the Euphotic Layer of the Northern Black Sea in Summer, 2018 (Based on the Data of the 102nd Cruise of R/V "Professor Vodyanitsky")

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